Initial revision

From-SVN: r102074

libjava/classpath/java/rmi/server/RMIClassLoader.java

@@ -0,0 +1,339 @@
+/* RMIClassLoader.java --
+   Copyright (c) 1996, 1997, 1998, 1999, 2002, 2003, 2004
+   Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.rmi.server;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.Hashtable;
+import java.util.Map;
+import java.util.StringTokenizer;
+
+
+/**
+ * This class provides a set of public static utility methods for supporting
+ * network-based class loading in RMI. These methods are called by RMI's
+ * internal marshal streams to implement the dynamic class loading of types for
+ * RMI parameters and return values.
+ */
+public class RMIClassLoader
+{
+  /**
+   * This class isn't intended to be instantiated.
+   */
+  private RMIClassLoader() {}
+
+  private static class MyClassLoader extends URLClassLoader
+  {
+    // Package-private to avoid a trampoline constructor.
+    MyClassLoader (URL[] urls, ClassLoader parent, String annotation)
+    {
+      super (urls, parent);
+      this.annotation = annotation;
+    }
+
+    private MyClassLoader (URL[] urls, ClassLoader parent)
+    {
+      super (urls, parent);
+      this.annotation = urlToAnnotation (urls);
+    }
+
+    public static String urlToAnnotation (URL[] urls)
+    {
+      if (urls.length == 0)
+        return null;
+
+      StringBuffer annotation = new StringBuffer (64 * urls.length);
+
+      for (int i = 0; i < urls.length; i++)
+      {
+        annotation.append (urls [i].toExternalForm());
+        annotation.append (' ');
+      }
+
+      return annotation.toString();
+    }
+
+    public final String getClassAnnotation()
+    {
+      return annotation;
+    }
+
+    private final String annotation;
+  }
+  
+  /** 
+   * This class is used to identify a cached classloader by its codebase and 
+   * the context classloader that is its parent.
+   */  
+  private static class CacheKey
+  {
+     private String mCodeBase;
+     private ClassLoader mContextClassLoader;
+  	
+     public CacheKey (String theCodebase, ClassLoader theContextClassLoader)
+     {
+       mCodeBase = theCodebase;
+       mContextClassLoader = theContextClassLoader;
+     }
+  	
+    /**
+     * @return true if the codebase and the context classloader are equal
+     */
+    public boolean equals (Object theOther)
+    {
+      if (theOther instanceof CacheKey)
+      {
+      	CacheKey key = (CacheKey) theOther;
+	
+      	return (equals (this.mCodeBase,key.mCodeBase)
+                && equals (this.mContextClassLoader, key.mContextClassLoader));
+        }
+      return false;
+    }
+    
+    /**
+     * Test if the two objects are equal or both null.
+     * @param theOne
+     * @param theOther
+     * @return
+     */
+    private boolean equals (Object theOne, Object theOther)
+    {
+      return theOne != null ? theOne.equals (theOther) : theOther == null;
+    }
+
+    /**
+     * @return hashCode  
+     */
+    public int hashCode()
+    {
+      return ((mCodeBase != null           ? mCodeBase.hashCode()           :  0) 
+              ^(mContextClassLoader != null ? mContextClassLoader.hashCode() : -1));
+    }
+
+    public String toString()
+    {
+      return "[" + mCodeBase + "," + mContextClassLoader + "]"; 
+    }
+
+  }
+
+  private static Map cacheLoaders; //map annotations to loaders
+  private static Map cacheAnnotations; //map loaders to annotations
+
+  //defaultAnnotation is got from system property
+  // "java.rmi.server.defaultAnnotation"
+  private static String defaultAnnotation;
+
+  //URL object for defaultAnnotation
+  private static URL defaultCodebase;
+
+  //class loader for defaultAnnotation
+  private static MyClassLoader defaultLoader;
+
+  static
+  {
+    // 89 is a nice prime number for Hashtable initial capacity
+    cacheLoaders = new Hashtable (89);
+    cacheAnnotations = new Hashtable (89);
+
+    defaultAnnotation = System.getProperty ("java.rmi.server.defaultAnnotation");
+
+    try
+      {
+        if (defaultAnnotation != null)
+          defaultCodebase = new URL (defaultAnnotation);
+      }
+    catch (Exception _)
+      {
+        defaultCodebase = null;
+      }
+
+    if (defaultCodebase != null)
+      {
+        defaultLoader = new MyClassLoader (new URL[] { defaultCodebase }, null,
+                                           defaultAnnotation);
+        cacheLoaders.put (new CacheKey (defaultAnnotation,
+                                        Thread.currentThread().getContextClassLoader()),
+                                        defaultLoader);
+      }
+    }
+
+  /**
+   * @deprecated
+   */
+  public static Class loadClass (String name)
+    throws MalformedURLException, ClassNotFoundException
+  {
+    return loadClass ("", name);
+  }
+
+  public static Class loadClass (String codebases, String name)
+    throws MalformedURLException, ClassNotFoundException
+  {
+    ClassLoader loader = Thread.currentThread().getContextClassLoader();
+
+    //try context class loader first
+    try 
+      {
+        return loader.loadClass (name);
+      }
+    catch (ClassNotFoundException e)
+      {
+        // class not found in the local classpath
+      }
+
+    if (codebases.length() == 0) //==""
+      {
+        loader = defaultLoader;
+      }
+    else
+      {
+        loader = getClassLoader(codebases);
+      }
+
+    if (loader == null)
+      {
+        //do not throw NullPointerException
+        throw new ClassNotFoundException ("Could not find class (" + name +
+                                          ") at codebase (" + codebases + ")");
+      }
+      
+    return loader.loadClass (name);
+  }
+
+  /**
+   * Gets a classloader for the given codebase and with the current
+   * context classloader as parent.
+   * 
+   * @param codebases
+   * 
+   * @return a classloader for the given codebase
+   * 
+   * @throws MalformedURLException if the codebase contains a malformed URL
+   */
+  public static ClassLoader getClassLoader (String codebases) 
+    throws MalformedURLException
+  {
+    ClassLoader loader;
+    CacheKey loaderKey = new CacheKey
+      (codebases, Thread.currentThread().getContextClassLoader());
+    loader = (ClassLoader) cacheLoaders.get (loaderKey);
+      
+    if (loader == null)
+      {
+        //create an entry in cacheLoaders mapping a loader to codebases.
+        // codebases are separated by " "
+        StringTokenizer tok = new StringTokenizer (codebases, " ");
+        ArrayList urls = new ArrayList();
+      
+        while (tok.hasMoreTokens())
+          urls.add (new URL (tok.nextToken()));
+      
+        loader = new MyClassLoader ((URL[]) urls.toArray (new URL [urls.size()]),
+                                    Thread.currentThread().getContextClassLoader(),
+                                    codebases);
+        cacheLoaders.put (loaderKey, loader);
+      }
+           
+    return loader;
+  }
+ 
+  /**
+   * Returns a string representation of the network location where a remote
+   * endpoint can get the class-definition of the given class.
+   *
+   * @param cl
+   *
+   * @return a space seperated list of URLs where the class-definition
+   * of cl may be found
+   */
+  public static String getClassAnnotation (Class cl)
+  {
+    ClassLoader loader = cl.getClassLoader();
+    
+    if (loader == null
+        || loader == ClassLoader.getSystemClassLoader())
+      {
+        return System.getProperty ("java.rmi.server.codebase");
+      }
+
+    if (loader instanceof MyClassLoader)
+      {
+        return ((MyClassLoader) loader).getClassAnnotation();
+      }
+
+    String s = (String) cacheAnnotations.get (loader);
+
+    if (s != null)
+      return s;
+
+    if (loader instanceof URLClassLoader)
+      {
+        URL[] urls = ((URLClassLoader) loader).getURLs();
+
+        if (urls.length == 0)
+          return null;
+
+        StringBuffer annotation = new StringBuffer (64 * urls.length);
+
+        for (int i = 0; i < urls.length; i++)
+          {
+            annotation.append (urls [i].toExternalForm());
+            annotation.append (' ');
+          }
+
+        s = annotation.toString();
+        cacheAnnotations.put (loader, s);
+        return s;
+      }
+
+    return System.getProperty ("java.rmi.server.codebase");
+  }
+
+  /**
+   * @deprecated
+   */
+  public static Object getSecurityContext (ClassLoader loader)
+  {
+    throw new Error ("Not implemented");
+  }
+}